The present invention relates towards systems and method for stents. More particularly, the invention relates to a stent designed to increase patient comfort by minimizing irritation and reflux through the use of a stent that incorporates one or more flexible elements, which may involve materials with varying degrees of hardness, and a valve disposed therein.
Stents are thin, hollow tubes inserted into a conduit in a patient to assist in opening a passageway that has been obstructed, or to assist in maintaining a passageway between two localized areas in the patient. Stents may be used to prevent flow constriction and to allow access for surgical procedures. One specific type of stent, a ureteral stent, is used to maintain a passageway between a patient's kidneys and bladder due to complications from infection, tumors, kidney stones, or other conditions that impact the urinary tract. In particular, a ureteral stent is inserted into the ureter to assist in draining urine from the patient's kidney to the patient's bladder if there is a blockage or other condition that does not allow for normal urine flow. Stents are also routinely inserted into a patient's ureter for several days after ureteroscopic kidney stone surgery to remove kidney or ureteral stones. Stents are designed to be positioned within a patient for days or weeks until the blockage is removed or normal urine flow is otherwise restored.
There are numerous problems and side effects associated with existing ureteral stents, however. One such problem is migration of the stent after insertion such that the stent does not remain in the specified location over the duration that the stent is disposed within the patient. To combat migration issues in stents, typical ureteral stent designs (e.g., double J) utilize coils at opposing proximal and distal ends of the stent to anchor the stent in the patient's kidney and bladder, respectively. Stents utilizing a double J design are more successful in retaining the ureteral stent in the desired location in the patient, but cause various other undesirable side effects due to the lower coil being disposed adjacent to and aggravating the patient's bladder. For example, the lower coil frequently causes the patient to suffer from bleeding, urges to pass urine frequently, and burning while passing urine due to the coil scratching the bladder.
An additional consideration for a ureteral stent is the desirability to control urine reflux that occurs during urination while using a stent. Stents frequently include at least one hollow tube (e.g., a lumen) so typically some amount of urine refluxes back into the patient's kidneys during and after urination as opposed to exiting from the body. Existing ureteral stents have insufficient mechanisms to control reflux that also allow for urine flow to pass from the patient. Reflux may cause pain (sometimes severe) in some patients and may lead to serious health conditions including urinary tract infections and even renal failure in extreme cases.
Attempts have been made to modify ureteral stent design to overcome the aforementioned problems to prohibit migration of the stent while minimizing patient discomfort. For example, one such stent incorporates a coiled end portion designed to reside in the patient's kidney and terminates at one or more flexible loops. The stent is substantially rigid throughout the length thereof until terminating at the loops. However, significant drawbacks exist with this stent design. For example, the stent includes a significant portion of rigid material that irritates the patient's urinary tract and results in patient discomfort. Further, this stent design does not include a mechanism to control reflux.